As disclosed e.g. in Japanese Patent Publication Toku Kai Hei No. 7-111053, the hard disc drive apparatus to be used as a memory or storage device for computers etc. has a structure as shown in FIG. 23. The hard disc drive apparatus comprises a hard disc 1, a swing arm 3 with a head 2 at the tip end thereof and a rolling bearing 4 as shown e.g. in FIG. 24. The hard disc 1 is rotated at a high speed by an electric motor of the direct drive type when the hard disc drive apparatus is used. This electric motor has a drive shaft, which is a base end portion of the swing arm 3 with the head 2. The drive shaft of the electric motor or the base end portion of the swing arm 3 is supported by the rolling bearing 4 so as to be rotated with reference to the motor case or to be rockingly displaced with reference to the support shaft.
The rolling bearing 4 comprises an outer ring 6 having an inner peripheral surface on which an outer ring raceway 5 is formed, an inner ring 8 having an outer peripheral surface on which an inner ring raceway 7 is formed, a plurality of rolling members 9 rotatably provided between the outer ring raceway 5 and the inner ring raceway 7, and a pair of shield plates 11 each provided on either side of the rolling bearing 4.
The rolling bearing 4 is formed with a space 14 between the inner peripheral surface of the outer ring 6 and the outer peripheral surface of the inner ring 8 to accommodate the rolling members 9 therein, and the shield or seal plates 11 as shown in FIGS. 24 and 25 and in FIGS. 26 to 28 are conventionally used in order to close the opening at either axial end of the space 14.
The rolling members 9 are arranged in a circumferential direction and supported by a cage 10, which is e.g. of a corrugated type made of a metal or of a crown type made of synthetic resin. The shield plates 11 have an outer peripheral edge portion which is anchored on the inner peripheral surface at either axial end portion of the outer ring 6, and an inner peripheral edge portion located close to the outer peripheral surface at either end portion of the inner ring 8, so that the space portion accommodating the rolling members 9 is isolated from outside.
In the rolling bearing 4 illustrated in FIG. 24, the outer ring 6 is formed with an anchor groove 12 on the inner peripheral surface at either axial end thereof, and the shield plates 11 are fixed to the outer ring 6 by crimping the outer peripheral portion thereof into the anchor grooves 12. Specifically, the shield plates 11 are made of a metal sheet in a generally circular ring shape, and the outer peripheral edge portion of the shield plates 11 is formed with a lapel portion 13 in a substantially semicircular shape in cross section. The lapel portion 13 is then positioned on the radially inner side of the groove 12, and in this state, plastically deformed radially outwards, that is widened by crimping. Consequently, the outer peripheral portion of the shield plates 11 is anchored in the groove 12 as shown in FIGS. 24 and 25.
The seal plates 11a in FIG. 26 comprises an elastic member 15a such as rubber and a metal member 16a for reinforcement on the inside of the elastic member 15a while the seal plate 11b in FIG. 27 comprises an elastic member 15b such as rubber and a metal member 16b for reinforcement on the outside of the elastic member 15b. The outer peripheral edge portion of the elastic member 15a in the seal plate 11a is projected radially outward from the outer peripheral edge of the metal member 16a with this projected portion anchored by way of its elasticity into the groove 12 on the inner peripheral surface at the axial end of the outer ring 6 while the outer peripheral edge portion of the elastic member 15b in the seal plate 11b is projected radially outward from the outer peripheral edge of the metal member 16b with this projected portion anchored by way of its elasticity into the groove 12 on the inner peripheral surface at the axial end of the outer ring 6. Thus, the seal plates 11a, 11b are anchored on the inner peripheral surface at the axial end of the outer ring 6, respectively.
The seal plate 11c in FIG. 28 is made of a metal sheet and formed with a lapel portion 13a along the outer peripheral edge portion thereof, and an elastic member 17 made of organic material such as rubber, elastomer is attached to the substantially whole outer peripheral surface of the portion lapel 13. In the state where the outer peripheral edge portion of the seal plate 11c is anchored in the groove 12 on the inner peripheral surface at the axial end of the outer ring 6, the elastic member 17 is elastically compressed between the outer peripheral surface of the lapel portion 13a and the inside surface of the groove 12 to seal between the outer and inner peripheral surfaces.
Some improvements are required in the conventional rolling bearings with shield plate having shield or seal plates as shown in FIGS. 24 to 28 (depicted by 11, 11c, 11a, 11b) as follows;
In the structure as illustrated in FIGS. 24 and 25, the seal performance between the outer peripheral edge portion of the shield plate 11 and the inside surface of the groove 12 is not sufficient, so that the grease and the base oil component of the grease filled in the space 14 may leak out through the seal portion between the outer peripheral edge portion of the shield plate 11 and the inside surface of the groove 12. Specifically, a minute clearance may exist due to the metal to metal contact relationship between the outer peripheral edge portion of the shield plate 11 and the inside surface of the groove 12. In addition, discontinuity portions 27 exist as shown in FIGS. 11, 13 in the midway of the lapel portion 13, and therefore any clearance is unavoidably produced. Consequently, the grease and/or the base oil component of the grease may leak out of the rolling bearing installed in the HDD or FDD through the minute clearance etc., and contaminate the installation space of the HDD or FDD which must be kept clean because the hard disc is installed therein. This may lead to malfunction of the computer devices with the HDD or FDD installed therein. This is not desirable.
In the case of the structures as shown in FIGS. 26 to 28, the grease and/or the base oil component of the grease is effectively prevented from leaking out of the rolling bearing having the shield plates, but on the other hand, debris of the elastic member may fly into the installation space which must be clean for the hard disc installed therein. Specifically, in the structures as shown in FIGS. 26 to 28, part of the elastic member (15a in FIG. 26, 15b in FIG. 27, and 17 in FIG. 28) of the shield or seal plate is exposed to the outside of the space 14. And when the outer peripheral edge portion of the shield or seal plate (11a in FIG. 26, 11b in FIG. 27, and 11c in FIG. 28) is fitted into the groove 12, the part of the elastic member may be broken to produce debris, which may contaminate the installation space which must be clean for the hard disc installed therein. When the elastic member is made of rubber, the additives or vulcanization agents contained in the rubber will contaminate the installation space. This is called chemical contamination. The utilization of fluorinated rubber for the elastic member or secondary vulcanization may solve the problems of the chemical contamination in a degree, but increase the material cost and process cost.